Group Size and Incentives to Contribute: A Natural Experiment at Chinese Wikipedia

In this paper, we examine the causal relationship between group size and incentives to contribute in the setting of Chinese Wikipedia, the Chinese language version of an online encyclopedia that relies entirely on voluntary contributions. The group at Chinese Wikipedia is composed of Chinese-speaking people in mainland China, Taiwan, Hong Kong, Singapore, and other regions in the world, who are aware of Chinese Wikipedia and have access to it. Our identification hinges on the exogenous reduction in group size at Chinese Wikipedia as a result of the block of Chinese Wikipedia in mainland China in October 2005. During the block, mainland Chinese could not use or contribute to Chinese Wikipedia, although contributors outside mainland China could continue to do so. We find that contribution levels of these nonblocked contributors decrease by 42.8 percent on average as a result of the block. We attribute the cause to social effects: contributors receive social benefits from their contributions, and the shrinking group size reduces these social benefits. Consistent with our explanation, we find that the more contributors value social benefits, the greater the reduction in their contributions after the block.